The invention relates to an improved light transceiver including an adjustable mirror for deflecting ambient light around the transceiver to improve the sensitivity of the transceiver's operation.
For an alarm or counting system to work efficiently ambient light interference must be sufficiently attenuated or interruptions of the light beam will not be noticed, because the receiver is still receiving sufficient illumination to maintain the light level above the threshold of the receiving device. The failure of counting systems to discern between two separate objects passing through a light screen and one object interrupting the light beam more than once as it passes through the screen also will result in an erroneous or false count.
The prior art has developed several light screen devices for counting objects passed through the screen. U.S. Pat. No. 3,025,406 shows a light screen or barrier for ballistic uses including an adjustable mirror for directing the reflected light. U.S. Pat. No. 3,327,942 provides a light frame counter in a laundry environment. U.S. Pat. Nos. 3,383,517 and 3,584,226 are directed to light frame counters which include different means for eliminating false counts from the counting circuit. The problem of ambient light which interferes with the efficient operation of these devices is not overcome in the prior art. One attempt to eliminate ambient light interference in the prior art is a tube extending from the light receiver with its axis aligned with the light axis of interest to attempt to attenuate the outside interference.